Reland "[parser] Set all tokens to ILLEGAL on parser error"

Fix: Skip sanity check of illegal tokens
Additional fix: set c0_ to kEndOfInput

Bug: v8:8363, v8:7926
Change-Id: I4f1222945914462e495d9ed6b86d38e478adbe39
Reviewed-on: https://chromium-review.googlesource.com/c/1304298
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57085}

src/parsing/parser-base.h

@@ -3365,7 +3365,8 @@ ParserBase<Impl>::ParseFunctionExpression() {
     // We don't want dynamic functions to actually declare their name
     // "anonymous". We just want that name in the toString().
     Consume(Token::IDENTIFIER);
-    DCHECK(scanner()->CurrentMatchesContextual(Token::ANONYMOUS));
+    DCHECK_IMPLIES(!has_error(),
+                   scanner()->CurrentMatchesContextual(Token::ANONYMOUS));
   } else if (peek_any_identifier()) {
     bool is_await = false;
     name = ParseIdentifierOrStrictReservedWord(
@@ -4420,9 +4421,9 @@ ParserBase<Impl>::ParseAsyncFunctionLiteral() {
 
     // Consuming token we did not peek yet, which could lead to a ILLEGAL token
     // in the case of a stackoverflow.
-    Expect(Token::IDENTIFIER);
-    RETURN_IF_PARSE_ERROR;
-    DCHECK(scanner()->CurrentMatchesContextual(Token::ANONYMOUS));
+    Consume(Token::IDENTIFIER);
+    DCHECK_IMPLIES(!has_error(),
+                   scanner()->CurrentMatchesContextual(Token::ANONYMOUS));
   } else if (peek_any_identifier()) {
     type = FunctionLiteral::kNamedExpression;
     bool is_await = false;

src/parsing/scanner.cc

@@ -408,6 +408,7 @@ void Scanner::SanityCheckTokenDesc(const TokenDesc& token) const {
 
   switch (token.token) {
     case Token::UNINITIALIZED:
+    case Token::ILLEGAL:
       // token.literal_chars & other members might be garbage. That's ok.
       break;
     case Token::TEMPLATE_SPAN:

src/parsing/scanner.h

@@ -238,7 +238,16 @@ class Scanner {
 
   // Sets the Scanner into an error state to stop further scanning and terminate
   // the parsing by only returning ILLEGAL tokens after that.
-  V8_INLINE void set_parser_error() { source_->set_parser_error(); }
+  V8_INLINE void set_parser_error() {
+    if (!source_->has_parser_error()) {
+      c0_ = kEndOfInput;
+      source_->set_parser_error();
+      for (TokenDesc& desc : token_storage_) {
+        desc.token = Token::ILLEGAL;
+        desc.contextual_token = Token::UNINITIALIZED;
+      }
+    }
+  }
   V8_INLINE void reset_parser_error_flag() {
     source_->reset_parser_error_flag();
   }